Light emitting element

ABSTRACT

A light emitting element includes a semiconductor structure layer, a reflective electrode layer formed on a part of the semiconductor structure layer, a conductor layer formed on the semiconductor structure layer with the reflective electrode layer embedded therein, and a support substrate that is arranged on the conductor layer and joined to the conductor layer via a junction layer. A high resistance contact surface is provided at an interface between the semiconductor structure layer and the conductor layer. A high resistance portion is arranged in an area opposed via the conductor layer to an area where the high resistance contact surface is provided. The conductor layer is connected to the junction layer in a peripheral area of the conductor layer outside the high resistance portion.

This application claims the priority benefit under 35 U.S.C. §119 ofJapanese Patent Application No. 2012-234555 filed on Oct. 24, 2012,which is hereby incorporated in its entirety by reference.

TECHNICAL FIELD

The present invention relates to a light emitting element such as alight emitting diode (LED).

BACKGROUND ART

Light emitting elements such as an LED element have conventionally beenused in light emitting apparatuses that are used for lighting,backlight, industrial equipment, and the like. Some such light emittingelements can include a reflective electrode layer made of Ag or thelike, which is formed on a surface opposite to a light emission surfaceof a semiconductor structure layer including an active layer. Ag andother materials used for the reflective electrode layer are prone toelectromigration. The electromigration refers to the diffusion andmovement of Ag and the like in the LED element due to an electric fieldand/or a current flow. For such a reason, an anti-diffusion layer isformed around the reflective electrode layer (see Japanese PatentApplication Laid-Open Nos. Hei. 11-220171, 2007-080899, and2007-335793).

Low-profile high-output LED elements have been used recently. In such anLED element, a high current flowing into the element may diffuse themetal components forming the reflective electrode layer, such as Ag andAl, such that the metal components are pushed out along the surface ofthe semiconductor structure layer. This may reduce the density of thereflective electrode layer to lower the reflectance at the surface ofthe reflective electrode layer. In addition, the current density in thesemiconductor structure layer becomes uneven, which reduces the emissionefficiency of the light emitting element. The metal components can bediffused to and deposited on the side surfaces of the semiconductorstructure layer, in which case the semiconductor structure layer isshort-circuited to cause a lighting failure and the like of the lightemitting element.

SUMMARY

The present invention was devised in view of these and other problemsand features and in association with the conventional art. According toan aspect of the present invention, a light emitting element is providedin which the diffusion of a metal material forming a reflectiveelectrode layer along the surface of a semiconductor structure layer issuppressed to prevent a drop in emission efficiency and improvereliability.

A light emitting element according to the present invention can include:a semiconductor structure layer; a reflective electrode layer that isformed on a part of the semiconductor structure layer; a conductor layerthat is formed on the semiconductor structure layer so that thereflective electrode layer is embedded therein; a support substrate thatis provided on the conductor layer and joined to the conductor layerwith a junction layer interposed therebetween; a high resistance contactsurface that is provided at an interface between the semiconductorstructure layer and the conductor layer; and a high resistance portionthat is provided in an area opposed via the conductor layer to an areawhere the high resistance contact surface is provided, wherein theconductor layer being connected to the junction layer in a peripheralarea of the conductor layer outside the high resistance portion.

In the light emitting element as described above, the semiconductorstructure layer can include a current inhibition portion that extendsfrom the high resistance contact surface to inside.

In the light emitting element as described above, the high resistanceportion can be a gap.

In the light emitting element as described above, an ohmic electrodelayer can be formed between the reflective electrode layer and thesemiconductor structure layer.

In the light emitting element as described above, the reflectiveelectrode layer may extend to over the high resistance contact surface.

In this case, the reflective electrode layer may extend over the highresistance contact surface up to a position reaching an area between thehigh resistance contact surface and the high resistance portion.

The light emitting element as described above can be configured suchthat a distance between an inner edge and an outer edge of a connectionsurface between the conductor layer and the high resistance portion inthe peripheral area of the conductor layer outside the high resistanceportion is greater than a distance between a top surface of the highresistance portion and the high resistance contact surface.

The light emitting element as described above can further include aninsulator that covers a side surface of the semiconductor structurelayer and an end area of a surface of the semiconductor layer in contactwith the conductor layer.

In the light emitting element of the aspect of the present invention,the junction layer can have a gap in an area opposed to an area wherethe high resistance contact surface is formed via the conductor layer.

In the light emitting element of the aspect of the present invention,the current inhibition portion can be formed by applying plasmaprocessing to the semiconductor structure layer.

In the light emitting element of the aspect of the present invention,the conductor layer and the semiconductor structure layer may form aSchottky junction.

BRIEF DESCRIPTION OF DRAWINGS

These and other characteristics, features, and advantages of the presentinvention will become clear from the following description withreference to the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view of a light emitting element accordingto a first exemplary embodiment of the present invention;

FIG. 2 is a partial enlarged view of the cross-sectional view of FIG. 1;

FIGS. 3A to 3D are diagrams showing manufacturing steps of the lightemitting element of FIG. 1;

FIG. 4 is a cross-sectional view of a light emitting element accordingto a second exemplary embodiment of the present invention;

FIGS. 5A to 5C are diagrams showing manufacturing steps of the lightemitting element of FIG. 4;

FIG. 6 is a cross-sectional view of a light emitting element accordingto a third exemplary embodiment of the present invention;

FIG. 7 is a cross-sectional view of a light emitting element accordingto a fourth exemplary embodiment of the present invention; and

FIG. 8 is a cross-sectional view of a light emitting element accordingto another exemplary embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A description will now be made below to vehicle lights of the presentinvention with reference to the accompanying drawings in accordance withexemplary embodiments.

First Exemplary Embodiment

Referring to FIGS. 1 and 2, a light emitting element 10 according to afirst exemplary embodiment of the present invention will be describedbelow by using an LED element as an example. FIG. 1 is a cross-sectionalview of the light emitting element 10 according to the first exemplaryembodiment of the present invention. FIG. 2 is a partial enlarged viewof a right end portion of the cross-sectional view of FIG. 1.

A support substrate 11 is a conductive substrate made of, for example,boron-doped Si. The support substrate 11 may be made of other materialshaving electrical conductivity and high thermal conductivity. Examplesmay include Ge, Al, Cu, and CuW. A metal film (not shown) intended toimprove bonding characteristics for mounting the light emitting element10 on a light emitting apparatus may be formed on the back side of thesupport substrate 11. For example, the metal film may be formed bystacking Ti, Pt, Au, and the like in order on the back surface of thesupport substrate 11.

A junction layer 13 is a metal layer formed by stacking Ti, Pt, and Auin order on the top surface of the support substrate 11. The junctionlayer 13 is joined to a conductive protection layer 15 above by theapplication of heat and pressure. The conductive protection layer 15arranged on the junction layer 13 is a conductor layer joined to thejunction layer 13. The conductive protection layer 15 is a metal layerincluding Au, Pt, Ti, and TiW stacked in order from the junction layer13 side. In other words, the support substrate 11 is joined to theconductive protection layer 15 via the junction layer 13.

A high resistance portion 17 is formed in a peripheral area of theconductive protection layer 15. For example, the high resistance portion17 is a tube-like space or gap formed by a recess of the conductiveprotection layer 15 and the junction layer 13 covering the opening. Thehigh resistance portion 17 may be continuously formed along theperiphery of the conductive protection layer 15. The high resistanceportion 17 may be discretely formed in certain lengths. The highresistance portion 17 is an area having a resistance higher than that ofthe other portions of the conductive protection layer 15. A current fromthe junction layer 13 flows into the conductive protection layer 15through the portions other than the high resistance portion 17. Anelectrical contact surface formed on the outermost periphery of theinterface between the junction layer 13 and the conductive protectionlayer 15, lying outside the high resistance portion 17, will be referredto as a peripheral contact surface 19. The high resistance potion 17 hasa width W1 of, for example, 5 μm. The peripheral contact surface 19 hasa width W2 of, for example, 10 μm. The conductive protection layer 15above the high resistance portion 17 has a thickness of, for example,900 nm. The high resistance portion 17 may be filled with a materialhaving a resistance higher than that of the materials forming theconductive protection layer 15. For example, the high resistance portion17 may be filled with a high resistance material such as SiO₂ and SiN.

The conductive protection layer 15 has a recess which extends from thecenter of the top surface toward the edges of the conductive protectionlayer 15. A reflective electrode layer 21 is formed in the recess. Thereflective electrode layer 21 is a metal layer made of metal having highlight reflectivity, such as Ag. The reflective electrode layer 21 isarranged to fill the recess of the conductive protection layer 15. Thetop surface of the reflective electrode layer 21 forms a flat surfacewith the conductive protection layer 15. A semiconductor structure layer23 is formed on the flat surface. In other words, the reflectiveelectrode layer 21 is formed in contact with the surface of thesemiconductor structure layer 23, and the conductive protection layer 15is formed so that the reflective electrode layer 21 is embedded therein.The reflective electrode layer 21 serves to reflect light emitted fromthe semiconductor structure layer 23. The reflective electrode layer 21also functions as a p electrode when supplying power to thesemiconductor structure layer 23.

As described above, the semiconductor structure layer 23 is formed onthe conductive protection layer 15 and the reflective electrode layer21. The semiconductor structure layer 23 is configured so that a p-typesemiconductor layer 25, an active layer 27, and an n-type semiconductorlayer 29 are stacked from the reflective electrode layer 21 side. Thep-type semiconductor layer 25 includes a p-type GaN layer and a p-typeAlGaN layer. The active layer 27 has a multiple quantum well (MQW)structure. The n-type semiconductor layer 29 includes a strainrelaxation layer including GaN/InGaN, an n-type GaN layer, an undopedGaN layer, and a GaN buffer layer. The undoped GaN layer and the GaNbuffer layer are layers used to favorably grow the crystals of thesemiconductor structure layer 23. As for the light emitting element 10,the undoped GaN layer and the GaN buffer layer may be removed by using atechnique such as grinding, polishing, and reactive ion etching (RIE).

The p-type semiconductor layer 25 includes a current inhibition portion31 extending into the inside of the p-type semiconductor layer 25 in thearea which is in contact with the conductive protection layer 15. Forexample, the current inhibition portion 31 is formed by increasing theresistance of the area of the p-type semiconductor layer 25 in contactwith the conductive protection layer 15 by plasma processing. Thecurrent inhibition portion 31 has a resistance higher than that of theother portions of the p-type semiconductor layer 25. The interfacebetween the conductive protection layer 15 and the current inhibitionportion 31 constitutes a high resistance contact surface 32. The highresistance contact surface 32 has a contact resistance higher than thatof the interface between the reflective electrode layer 21 and theportion of the p-type semiconductor layer 25 where the currentinhibition portion 31 is not formed. Consequently, the current flowingfrom the junction layer 13 into the conductive protection layer 15 flowsinto the p-type semiconductor layer 25 via the portions other than thecurrent inhibition portion 31, i.e., without the intermediary of thehigh resistance contact surface 32. The p-type semiconductor layer 25 isformed in a thickness of, for example, 100 to 200 nm. The currentinhibition portion 31 is formed to extend from the surface into theinside of the p-type semiconductor layer 25. For example, the p-typesemiconductor layer 25 has a thickness T1 of 10 nm or greater. Forreliable current inhibition, a thickness T1 of 50 nm or greater isdesirable. The current inhibition portion 31 may be formed by applyingion implantation, reverse sputtering, and the like to the surface of thep-type semiconductor layer 25.

The active layer 27 is configured as a multiple quantum well (MQW),whereas it may be a single quantum well (SQW) or a single layer(so-called bulk layer). For example, the multiple quantum well structureincludes five pairs of a well layer and a barrier layer, with anIn_(x)Ga_(1-x)N layer (composition x=0.35; 2 nm in thickness) as thewell layer and a GaN layer (14 nm in thickness) as the barrier layer.The composition x of the In in the well layers is adjusted within therange of 0<x≦1.0 according to the emission wavelength.

An n electrode 33 is formed on the n-type semiconductor layer 29 of thesemiconductor structure layer 23. The n electrode 33 is formed bystacking Ti, Al, Ti, and Au in order on a part of the top surface of then-type semiconductor layer 29.

FIG. 2 shows an enlarged view of the vicinity of the high resistanceportion in FIG. 1. Thick arrows represent a current flowing in from theperipheral contact surface 19. As shown in FIG. 2, the light emittingelement 10 includes the high resistance contact surface 32 which isformed by forming the current inhibition portion 31 in the area of thesemiconductor structure layer 23 in contact with the conductiveprotection layer 15. The high resistance portion 17 is arranged at leastin a part of the area opposed to the current inhibition portion 31 viathe conductive protection layer 15. The high resistance portion 17 isformed by a recess of the conductive protection layer 15 and thejunction layer 13 covering the opening. The peripheral contact surface19 is formed outside the high resistance portion 17. With such aconfiguration, the light emitting element 10 produces a current flowtoward the center of the light emitting element 10 in the end area ofthe conductive protection layer 15. Specifically, the current flows fromthe peripheral contact surface 19 into the conductive protection layer15. The current passes through the area A (area enclosed by anddiagonally hatched with broken lines) sandwiched between the highresistance portion 17 and the high resistance contact surface 32 formedby the current inhibition portion 31. The current then flows into thereflective electrode layer 21 and to the p-type semiconductor layer 25.In other words, a current path directed toward the inside of the lightemitting element 10 along the interface between the conductiveprotection layer 15 and the semiconductor structure layer 23 is formedin the conductive protection layer 15.

The metal material of the reflective electrode layer 21 is beingdiffused toward the outside of the element along the interface betweenthe conductive protection layer 15 and the semiconductor structure layer23. The current flow toward the inside of the light emitting element 10along the interface between the conductive protection layer 15 and thesemiconductor structure layer 23 causes electromigration that moves sucha metal material as if the metal material is pushed back toward theinside of the element.

In the light emitting element 10, the occurrence of the electromigrationtoward the inside of the element pushes back Ag, which is being diffusedtoward the outside of the element along the interface between theconductive protection layer 15 and the semiconductor structure layer 23,toward the inside of the element. As a result, the diffusion of thematerial forming the reflective electrode layer 21 toward the outside ofthe light emitting element 10 is suppressed. This prevents a drop in theemission efficiency of the light emitting element 10, a lighting failureof the light emitting element 10, and the like due to degradation of thereflective electrode layer 21. As a result, the reliability of the lightemitting element 10 can be improved.

In the foregoing description, the high resistance portion 17 may befilled with a high resistance material. To raise the temperature nearthe interface between the conductive protection layer 15 and thesemiconductor structure layer 23 to provide an environment for promotingelectromigration, the high resistance portion 17 desirably has a highthermal resistance. Thus, the high resistance portion 17 is desirablyleft vacant.

To increase the current density in the area A to promoteelectromigration, the peripheral contact surface 19 desirably has anarea greater than the cross-sectional area of the area A taken along theplane perpendicular to the current direction, i.e., the cross sectionperpendicular to the top surface of the support substrate 11 andperpendicular to the plane of FIG. 2. To satisfy such a condition, theperipheral contact surface 19 may have a width W2 greater than thethickness of the conductive protection layer 15. More specifically, thedistance W2 between the inner edge and outer edge of the peripheralcontract surface 19 may be greater than the distance W3 between the topsurface of the high resistance portion 17 and the high resistancecontact surface 32.

A method for manufacturing the foregoing light emitting element 10 willbe described below with reference to FIGS. 3A to 3D. For the sake ofclarity, FIGS. 3A to 3D show the cross sections of three light emittingelements. In actual manufacturing, an array of a large number of lightemitting elements may be manufactured in a sheet-like configuration.

As shown in FIG. 3A, a growth substrate 35 such as a sapphire substrateis initially prepared. A semiconductor structure layer 23 is depositedby MOCVD. Specifically, for example, the growth substrate 35 is set inan MOCVD system. After thermal cleaning, an n-type semiconductor layer29 including a GaN buffer layer, an undoped GaN layer, and an n-type GaNlayer, an active layer 27, and a p-type semiconductor layer 25 includinga p-type AlGaN layer and a p-type GaN layer are deposited in order. Thegrowth substrate 35 on which the semiconductor structure layer 23 isdeposited is then heated in an RTA apparatus at 700° C. for one minuteto activate the p-type semiconductor layer 25.

Next, as shown in FIG. 3B, reflective electrode layers 21 are depositedon the p-type semiconductor layer 25. Specifically, for example, an Aglayer for forming the reflective electrode layers 21 is deposited in athickness of approximately 150 nm by using sputtering (for example,using a DC magnetron sputterer). A photoresist is applied to the surfaceof the formed Ag layer, and shaped into a desired pattern by using aphotolithographic technique. By using an Ag etching solution (forexample, an etchant formed by mixing nitric acid, water, acetic acid,and phosphoric acid in the ratio of 1:1:8:10), the Ag layer deposited onareas of the p-type semiconductor layer 25 where to form currentinhibition portions 31 (or high resistance contact surfaces 32) isremoved. The photoresist is removed to form the reflective electrodelayers 21 of desired pattern. Finally, annealing is performed in an RTAapparatus to ensure ohmic contact between the reflective electrodelayers 21 and the p-type semiconductor layer 25.

The deposition of the reflective electrode layers 21 is not limited tothe foregoing sputtering method, and may be performed by using othertechniques such as an electron beam (EB) method and a resistance heatingmethod. The reflective electrode layers 21 may be formed by lift-off.The lift-off includes forming a photoresist on areas of the p-typesemiconductor layer 25 where the reflective electrode layers 21 are notto be formed, then depositing an Ag layer, and removing the unnecessaryportions of the Ag layer with the photoresist.

Next, current inhibition portions 31 are formed in the p-typesemiconductor layer 25. Specifically, for example, plasma processing orreverse sputtering processing is performed on the p-type semiconductorlayer 25 where the reflective electrode layers 21 are not formed. Forexample, the reverse sputtering processing is performed in an RFsputterer by using Ar gas as an inert gas, at an Ar gas flow rate of 50sccm and power of 50 to 150 W for one to five minutes. The reversesputtering processing makes the p-type semiconductor layer 25 partlynonconductive to form the current inhibition portions 31. The areas ofthe p-type semiconductor layer 25 subjected to the reverse sputteringbecome nonconductive. Note that the current inhibition portions 31 maybe formed by performing ion implantation or other plasma processingusing an RIE system or the like, on the surface of the p-typesemiconductor layer 25.

Next, as shown in FIG. 3C, conductive protection layers 15 are formed onthe reflective electrode layers 21 and the surrounding p-typesemiconductor layer 25 so as to cover the reflective electrode layers21. Specifically, for example, a photoresist is applied onto thereflective electrode layers 21 and the p-type semiconductor layer 25.The photoresist is exposed and developed in a desired pattern. With thephotoresist pattern left on the areas where the conductive protectionlayers 15 are not to be formed, TiW (250 nm in thickness), Ti (50 nm inthickness), Pt (100 nm in thickness), and Au (500 nm in thickness) aredeposited and stacked in order by sputtering. The metals of theunnecessary portions are removed with the photoresist by lift-off. Usingthe same lift-off method as described above, Au is deposited in athickness of 150 nm on the outer edges of the formed metal layers whereto form the peripheral contact surfaces 19 with junction layers 13. Thiscompletes the conductive protection layers 15. The completed conductiveprotection layers 15 have recesses 17A to be the high resistanceportions 17 near the ends. Like the reflective electrode layers 21, thedeposition of the conductive protection layers 15 is not limited to thesputtering method, and may be performed by an EB method, a resistanceheating method, or a combination of these. If the high resistanceportions 17 are not to be left as a gap but to be filled with anothermaterial, the recesses 17A may be filled with a material having aresistance higher than that of the conductive protection layers 15 afterthe formation of the conductive protection layers 15. Examples of such amaterial may include SiO₂ and SiN.

Next, a support substrate 11 on which junction layers 13 are formed inpositions corresponding to the surfaces of the conductive protectionlayers 15 is prepared. For example, the support substrate 11 is a Sisubstrate. The junction layers 13 are formed by stacking Ti (600 nm inthickness), Pt (50 nm in thickness), and Au (1000 nm in thickness) inorder on the support substrate 11 by electron beam deposition or thelike.

Next, with the surfaces of the junction layers 13 and the surfaces ofthe conductive protection layers 15 in contact with each other,thermocompression bonding is performed under a pressure of 30 kg/cm² ata temperature of 200° C. for one hour, whereby the support substrate 11is bonded. Subsequently, for example, the back side of the growthsubstrate 35 is irradiated with excimer laser in a laser lift-off (LLO)system. This removes the growth substrate 35 as shown in FIG. 3D. Theremoval of the growth substrate 35 is not limited to laser lift-off(LLO), and may be performed by using wet etching, dry etching,mechanical polishing, chemical mechanical polishing (CMP), or a methodcombined with at least one of these methods.

If the growth substrate 35 is removed by LLO, Ga produced by the LLO isthen removed by using hot water and the like. The GaN buffer layer andthe undoped GaN layer of the n-type semiconductor layer 29 at thesurface are removed by dry etching in an RIE system, whereby the n-typeGaN layer is exposed. The resultant is then immersed into an alkalisolution such as a tetramethylammonium hydroxide (TMAH) solution to forma hexagonal pyramidal structure on the surface of the exposed n-type GaNlayer. The formation of the hexagonal pyramidal structure after the LLOmay be performed by using any chemical agent as long as nitridesemiconductors can be etched. Alkali solutions such as KOH and NaOH maybe used.

After the end of the foregoing processing, a resist is formed on theareas of the semiconductor structure layer 23 where to form lightemitting elements. In a dry etching system, the portions of thesemiconductor structure layer 23 other than the areas where the resistis formed are removed to separate the semiconductor structure layer 23into individual areas. The resist is then removed. As shown in FIG. 3D,n electrodes 33 are formed on the exposed n-type semiconductor layers29. The n electrodes 33 are formed by depositing Ti (1 nm in thickness),Al (200 nm in thickness), Ti (1 nm in thickness), and Au (1000 nm inthickness) in order by electron beam deposition and the like. The nelectrodes 33 may be made of material that can form an ohmic junctionwith an n-type semiconductor. Examples thereof may include AuGeNi, AuGe,AuSn, and AuSnNi. Finally, dicing is performed for element singulation,whereby the light emitting elements 10 are completed.

Second Exemplary Embodiment

A light emitting element 40 according to a second exemplary embodimentof the present invention will be described below. As shown in FIG. 4,the light emitting element 40 has generally the same configuration asthat of the light emitting element 10 except that the light emittingelement 40 includes an insulating protection film made of an insulatorwhich covers the side surfaces of the element. The insulating protectionfilm 41 covers the entire side surfaces and the ends of the lowersurface of the semiconductor structure layer 23. The insulatingprotection film 41 is made of an insulator such as SiO₂, and has athickness of, for example, 150 nm.

The insulating protection film 41 is formed after the reflectiveelectrode layers 21 (for example, 150 nm in thickness) are formed, thecurrent inhibition portions 31 are formed, and the semiconductorstructure layer 23 is separated into individual areas as shown in FIG.5A like the first exemplary embodiment. To separate the semiconductorstructure layer 23 into individual areas, a resist is formed on thesemiconductor structure layer 23 and the reflective electrode layers 21.In a dry etching system, the portions of the semiconductor structurelayer 23 other than the areas where the resist is formed are removed toform grooves that reach the top surface of the growth substrate 35.

After the separation, insulating protection films 41 are formed, forexample, by depositing SiO₂ on the side surfaces and the end areas(peripheral areas) of the top surfaces of the semiconductor structurelayers 23 by sputtering. The insulating protection films 41 aredeposited in the same thickness as that of the reflective electrodelayers 21, i.e., 150 nm. To form high resistance portions, theinsulating protection films 41 and the reflective electrode layers 21are formed at a sufficient distance from each other (for example,separated by 5 μm). As shown in FIG. 5C, conductive protection layers 15are formed by the same method as in the first exemplary embodiment so asto cover the insulating protection films 41 and the reflective electrodelayers 21 formed on the top surfaces of the semiconductor structurelayers 23.

As described above, in the light emitting element 40 according to thesecond exemplary embodiment, the conductive protection layer 15 isformed to cover the insulating protection film 41 and the reflectiveelectrode layer 21. The insulating protection film 41 is formed on theends of the top surface of the semiconductor structure layer 23 in thesame thickness as that of the reflective electrode layer 21. Unlike thelight emitting element 10 of the first exemplary embodiment, the highresistance portion 17 can be formed without the formation of anadditional metal layer on the portion where to form the peripheralcontact surface 19. This can simplify the manufacturing steps.

Third Exemplary Embodiment

A light emitting element 50 according to a third exemplary embodiment ofthe present invention will be described below. As shown in FIG. 6, thelight emitting element 50 has generally the same configuration as thatof the light emitting element 10 except that there is an area where thejunction layer 13 does not exist on the support substrate 11. In thelight emitting element 50, the high resistance portion 17 is formed bypartly providing an area where the junction layer 13 is not formed onthe peripheral area of the support substrate 11.

In the light emitting element 50, the high resistance portion 17 isformed not by forming an additional metal layer on the portion where toform the peripheral contact surface 19 in the step of forming theconductive protection layer 15 of the light emitting element 10according to the first exemplary embodiment. Instead, the highresistance portion 17 is formed by forming an inner junction layer 13Aand a peripheral junction layer 13B on the support substrate 11. Theperipheral junction layer 13B is formed at a distance from the innerjunction layer 13A. In other words, in the light emitting element 50,the junction layer 13 is not formed in a part of the area opposed to thehigh resistance contact surface via the conductive protection layer 15,and the part is left as a gap. The peripheral junction layer 13B isformed to be thicker than the inner junction layer 13A as much as thethickness of the reflective electrode layer 21. The high resistanceportion 17 is formed as an area that lies between the inner junctionlayer 13A and the peripheral junction layer 13B and is defined by thesupport substrate 11, the inner junction layer 13A, the peripheraljunction layer 13B, and the conductive protection layer 15.

In the light emitting element 50, unlike in the light emitting element10 of the first exemplary embodiment, such formation of the highresistance portion 17 eliminates the need to form an additional metallayer on the portion where to form the peripheral contact surface 19.This can simplify the manufacturing steps. The junction layer 13 and theconductive protection layer 15 may be made of metals prone todeformation during thermocompression, such as AuZn and AuSn. Even insuch cases, the thicknesses of the inner junction layer 13A and theperipheral junction layer 13B and the distance therebetween can beincreased, i.e., the size of the high resistance portion 17 can beincreased to easily form the high resistance portion 17 withoutcrushing. This can extend the range of choices for the materials of thejunction layer 13 and the conductive protection layer 15.

The foregoing exemplary embodiments have dealt with the light emittingelements of thin film type in which electrical connections are made onthe top and bottom surfaces of the light emitting elements. However, thepresent invention is also applicable to a light emitting element of flipchip type in which electrical connections are made only on the bottomsurface like a light emitting element 60 shown in FIG. 7. As shown inFIG. 7, the light emitting element 60 includes an n electrode 43 in oneof the end areas (right in the diagram) of the semiconductor structurelayer 23. The n electrode 43 extends from the p-type semiconductor layer25 to the n-type semiconductor layer 29. The light emitting element 60further includes a sub mount 47 having two wiring patterns 45A and 45Bon its top surface. The wiring pattern 45A is in contact with and bondedto the conductive protection layer 15, and the wiring pattern 45B is incontact with and bonded to the n electrode 43, by thermocompression. Thehigh resistance portion 17 is formed as a gap surrounded by the wiringpattern 45A and the conductive protection layer 15.

Like a light emitting element 70 shown in FIG. 8, an ohmic electrodelayer 49 may be formed between the reflective electrode layer 21 and thep-type semiconductor layer 25 of the foregoing light emitting elements.The ohmic electrode layer 49 is made of ITO or the like, has a lowcontact resistance with respect to the p-type semiconductor layer 25,and has higher affinity to metal than the p-type semiconductor layer 25.Such a configuration can reduce the contact resistance between thereflective electrode layer 21 and the p-type electrode layer 25 toimprove the emission efficiency of the light emitting elements.

Since the reflective electrode layer 21 is deposited on the ohmicelectrode layer 49, the ohmic electrode layer 49 can be formed beforethe formation of the current inhibition portion 31 and the deposition ofthe reflective electrode layer 21. The reflective electrode layer 21 canthus be formed to extend over the high resistance contact surface 32. Asa result, the formation area of the reflective electrode layer 21 can beincreased to reflect the light emitted from the active layer 27 moreefficiently. This can improve the emission output of the light emittingelement.

The high resistance portion 17 may also be formed in the areas opposedto the ends of the reflective electrode layer 21 formed on the currentinhibition portion 31. In other words, the reflective electrode layer 21may be extended over the high resistance contact surface 32 to positionsreaching the areas between the high resistance contact surface 32 andthe high resistance portion 17. This can form current paths toward theinside of the element even in the end areas of the reflective electrodelayer 21. As a result, the diffusion of the material forming thereflective electrode layer 21 toward the outside of the element can bemore effectively suppressed with a further improvement in thereliability of the light emitting element.

The ohmic electrode layer 49 may be a so-called transparent conductivefilm which has a low contact resistance with respect to the p-typesemiconductor layer 25 and is transparent (has translucency). Examplesof the material of the transparent conductive film may include ZnO, IZO,and AnNi alloys. Aside from the transparent conductive film, the ohmicelectrode layer 49 may be a thin film of Ag, Pt, Rh, or the like whichcan make favorable electrical contact with the p-type semiconductorlayer 25.

In the foregoing exemplary embodiments, the high resistance contactsurface 32 is formed by forming the current inhibition portion 31 in thep-type semiconductor layer 25. However, the high resistance contactsurface 32 may be formed by forming a Schottky junction between thep-type semiconductor layer 25 and the conductive protection layer 15. Insuch a case, the current inhibition portion 31 may be omitted.

In the foregoing exemplary embodiments, the conductive protection layer15 is a metal layer formed by stacking Au, Pt, Ti, and TiW in order fromthe junction layer 13 side. However, a translucent conductive filmhaving an optical refractive index lower than that of the p-typesemiconductor layer 25 may be added to the surface of the conductiveprotection layer 15 in contact with the p-type semiconductor layer 25.Examples of the material of the translucent conductive film may includeITO, IZO, and ZnO. The interface between the translucent conductive filmand the p-type semiconductor layer can totally reflect light to reducethe light that reaches and is absorbed by the metal layer. This canfurther improve the emission output of the light emitting element.

In the foregoing exemplary embodiments, the reflective electrode layer21 is formed as a single-layer film of Ag. However, the reflectiveelectrode layer 21 may be made of a material such as an Ag alloy, Al,and an Al alloy which have high light reflectance. The reflectiveelectrode layer 21 may be a multilayer film instead of a single-layerfilm. The multilayer film may be formed by stacking an extremely thin(for example, 5 nm or less) adhesive layer of Ti, Ni, or the like oneither one or both of the top and bottom surfaces of the foregoing filmmade of Ag, an Ag alloy, Al, an Al alloy, or the like.

Various numerical values, sizes, materials, and the like in theforegoing exemplary embodiments are just an example, and may be selectedas appropriate according to the intended use, the used light emittingelement, etc.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the presently disclosedsubject matter without departing from the spirit or scope of thepresently disclosed subject matter. Thus, it is intended that thepresently disclosed subject matter cover the modifications andvariations of the presently disclosed subject matter provided they comewithin the scope of the appended claims and their equivalents. Allrelated art references described above are hereby incorporated in theirentirety by reference.

What is claimed is:
 1. A light emitting element comprising: asemiconductor structure layer; a reflective electrode layer that isformed on a part of the semiconductor structure layer; a conductor layerthat is formed on the semiconductor structure layer so that thereflective electrode layer is embedded therein; a support substrate thatis provided on the conductor layer and joined to the conductor layerwith a junction layer interposed therebetween; a high resistance contactsurface that is provided at an interface between the semiconductorstructure layer and the conductor layer; and a high resistance portionthat is provided in an area directly opposed, via the conductor layer,to an area where the high resistance contact surface is provided in adirection substantially perpendicular to the high resistance contactsurface, the conductor layer being connected to the junction layer in aperipheral area of the conductor layer outside the high resistanceportion.
 2. The light emitting element according to claim 1, wherein thesemiconductor structure layer includes a current inhibition portion thatextends from the high resistance contact surface to inside.
 3. The lightemitting element according to claim 2, wherein the high resistanceportion is a gap.
 4. The light emitting element according to claim 3,wherein an ohmic electrode layer is formed between the reflectiveelectrode layer and the semiconductor structure layer.
 5. The lightemitting element according to claim 4, wherein the reflective electrodelayer extends to over the high resistance contact surface.
 6. The lightemitting element according to claim 5, wherein the reflective electrodelayer extends over the high resistance contact surface up to a positionreaching an area between the high resistance contact surface and thehigh resistance portion.
 7. The light emitting element according toclaim 2, wherein an ohmic electrode layer is formed between thereflective electrode layer and the semiconductor structure layer.
 8. Thelight emitting element according to claim 7, wherein the reflectiveelectrode layer extends to over the high resistance contact surface. 9.The light emitting element according to claim 8, wherein the reflectiveelectrode layer extends over the high resistance contact surface up to aposition reaching an area between the high resistance contact surfaceand the high resistance portion.
 10. The light emitting elementaccording to claim 2, wherein the current inhibition portion is formedby applying plasma processing to the semiconductor structure layer. 11.The light emitting element according to claim 1, wherein the highresistance portion is a gap.
 12. The light emitting element according toclaim 11, wherein an ohmic electrode layer is formed between thereflective electrode layer and the semiconductor structure layer. 13.The light emitting element according to claim 12, wherein the reflectiveelectrode layer extends to over the high resistance contact surface. 14.The light emitting element according to claim 13, wherein the reflectiveelectrode layer extends over the high resistance contact surface up to aposition reaching an area between the high resistance contact surfaceand the high resistance portion.
 15. The light emitting elementaccording to claim 1, wherein an ohmic electrode layer is formed betweenthe reflective electrode layer and the semiconductor structure layer.16. The light emitting element according to claim 15, wherein thereflective electrode layer extends to over the high resistance contactsurface.
 17. The light emitting element according to claim 16, whereinthe reflective electrode layer extends over the high resistance contactsurface up to a position reaching an area between the high resistancecontact surface and the high resistance portion.
 18. The light emittingelement according to claim 1, wherein a distance between an inner edgeand an outer edge of a connection surface between the conductor layerand the junction layer in the peripheral area of the conductor layeroutside the high resistance portion is greater than a distance between atop surface of the high resistance portion and the high resistancecontact surface.
 19. The light emitting element according to claim 1,further comprising an insulator that covers a side surface of thesemiconductor structure layer and an end area of a surface of thesemiconductor layer in contact with the conductor layer.
 20. The lightemitting element according to claim 1, wherein the high resistancecontact surface is a surface formed of a Schottky junction between theconductor layer and the semiconductor structure layer.
 21. A lightemitting element comprising: a semiconductor structure layer; areflective electrode layer that is formed on a part of the semiconductorstructure layer; a conductor layer that is formed on the semiconductorstructure layer so that the reflective electrode layer is embeddedtherein; a support substrate that is provided on the conductor layer andjoined to the conductor layer with a junction layer interposedtherebetween; a high resistance contact surface that is provided at aninterface between the semiconductor structure layer and the conductorlayer; and a high resistance portion that is provided in an area opposedvia the conductor layer to an area where the high resistance contactsurface is provided, wherein the conductor layer is connected to thejunction layer in a peripheral area of the conductor layer outside thehigh resistance portion, and wherein the junction layer has a gap in anarea opposed to an area where the high resistance contact surface isformed via the conductor layer.